As well known, the Internet is a massive network of networks in which computers communicate with each other via use of different communication protocols. The Internet includes packet-routing devices, such as switches, routers and the like, interconnecting many computers. To support routing of information such as packets, each of the packet-routing devices typically maintains routing tables to perform routing decisions in which to forward traffic from a source computer, through the network, to a destination computer.
One way of forwarding information through a provider network over the Internet is based on MPLS (Multiprotocol Label Switching) techniques. In an MPLS-network, incoming packets are assigned a label by a so-called LER (Label Edge Router) receiving the incoming packets. The packets in the MPLS network are forwarded along a predefined Label Switch Path (LSP) defined in the MPLS network based, at least initially, on the label provided by a respective LER. At internal nodes of the MPLS-network, the packets are forwarded along a predefined LSP through so-called Label Switch Routers.
Each Label Switching Router (LSR) in an LSP between respective LERs in an MPLS-type network makes forwarding decisions based solely on a label of a corresponding packet. Depending on the circumstances, a packet may need to travel through many LSRs along a respective path between LERs of the MPLS-network. As a packet travels through a label-switching network, each LSR along an LSP strips off an existing label associated with a given packet and applies a new label to the given packet prior to forwarding to the next LSR in the LSP. The new label informs the next router in the path how to further forward the packet to a downstream node in the MPLS network eventually to a downstream LER that can properly forward the packet to a destination.
As well known, MPLS types of networks can support so-called Virtual Private Networks (VPNs). A VPN allows service providers to securely connect multiple customer sites over a common shared network. According to conventional applications, a VPN service uses virtual connections to keep a given customer's data private from other customers' data communicated through a shared network.
In addition to supporting VPNs, an MPLS network can support so-called Layer 2 MPLS VPNs known as Virtual Private Local area network Services (VPLS). Instead of connecting customer IP routers so that they can communicate over a shared IP backbone as if they were using their own private network, VPLS techniques enable a customer's LANs to be connected over a shared IP backbone as if they were connected to the same LAN segment, effectively creating a multipoint Ethernet VPN. One way to set up a VPLS is to employ a communication protocol such as BGP (Border Gateway Protocol).